Answer:
A. E(x) = 1/n×n(n+1)/2
B. E(x²) = 1/n
Step-by-step explanation:
The n candidates for a job have been ranked 1,2,3....n. Let x be the rank of a randomly selected candidate. Therefore, the PMF of X is given as
P(x) = {1/n, x = 1,2...n}
Therefore,
Expectation of X
E(x) = summation {xP(×)}
= summation {X×1/n}
= 1/n summation{x}
= 1/n×n(n+1)/2
= n+1/2
Thus, E(x) = 1/n×n(n+1)/2
Value of E(x²)
E(x²) = summation {x²P(×)}
= summation{x²×1/n}
= 1/n
Answer:
The number is 91
Step-by-step explanation:
Let x be the ones place digit and y be the tens place digit,
Then the number would be 10y + x,
We have,
y - x = 8
Possible values of y and x = { (8, 0), (9, 1) }
∵ 0 is not the digit of the number,
Hence, y = 9 and x = 1
Therefore, required number = 10(9) + 1 = 90 + 1 = 91
Answer:
It's 90 because we'll make it equal
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